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Old 9th Apr 2022, 9:29 pm   #1
bionicmerlin
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Default Gent and Co Water level meter

I bought this item at a local auction last weekend. It was incorrectly listed as a clock ,I had worked that out before hand that’s why I bought it .
I just wondered if anyone had any information on it. It must of had a special float switch. What sort of age. I would of guessed 1920s But then the coils have a clear plastic sleeve. Surely plastic wasn’t around at the time. I’m not sure to transformer is original as it’s not mounted squarely.
I have temporarily tested the coils at 20 volt and that appears to be about right.
I’m not sure what I’m going to do with it but I will get a new piece of glass in it and restore it very sympathetically . Andy
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Old 10th Apr 2022, 10:47 am   #2
Roger Ramjet
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Nice find Andy...

There is an underground reservoir on the top of a hill located at Tilton On The Hill Leicestershire. In the 70's you could dial a local number that would be automatically answered whereupon a sound similar to a clock being wound up followed by a series of "dings"' would be heard. I assume this represented the actual level or capacity of the reservoir at that time. AKA - dial in telemetry.

It's my bet that your find may have formed part of that type of / or similar set up.

Good luck with the restoration.

Rog
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Old 10th Apr 2022, 12:10 pm   #3
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Default Re: Gent and Co Water level meter

Celluloid was available in 1872, Urea Formaldehyde in 1919 and Catalin in 1927.

This is not a declaration of their first use.
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Old 20th Apr 2022, 4:33 pm   #4
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Default Re: Gent and Co Water level meter

Hello Andy,

Many years ago I bought a chart-recording water level clock at our local house clearance shop. It's similar to the 1706 shown below and the pictures come from this 1950s catalogue that was tucked inside.

No mention of voltages for the display units, but mentions you'd need "1 battery (approx 4 cells)".

The back pages of the catalogue have 3 pint Leclanche Cells or Porcelain Dry Cells or a transformer can be purchased with 200-250V AC inputs and (unhelpfully for you) secondaries of 4 - 8 - 12 or 8 -16- 24 V.

Sorry it doesn't answer your question fully, I think this 1950s equipment is a lot newer than what you've found.

Regards,

SR
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Old 25th Apr 2022, 10:12 pm   #5
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Default Re: Gent and Co Water level meter

Thank you everyone for your information.
Stuart . Thanks for taking the time to download those pics from your brochure. What a nice find. The last picture is not so clear . It looks like a 2 wire system using GPO lines is this correct.
Do you mind if I download those pictures and share with a friend of mine.
Just a update on my recorder . I have done a-bit of rewireing to make it safe . Removing the double fuses on the mains live and neutral And having a fuse just on the live. Also adding a fuse on the transformer secondary side.
I have been scratching my head for sometime as it uses just to wires to go to the float switch. I worked it out in the end I think.
I have tested my theory using diodes. It appears on your diagram it works on 2 wires as well
AC is send down one wire . With the return wire sending plus or minus DC back up the Return wire to a centre tap on the recorder rectifier. Depending on the polarity the current gos one of two ways through the rectifier operating the rise or fall relay . The main solenoids on the recorder work on AC through the relay. The float switch must of been accurate to stop nuisance triggering
Just a couple pics . One showing my diagram Andy
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Old 26th Apr 2022, 11:53 am   #6
Lucien Nunes
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Default Re: Gent and Co Water level meter

This is a very nice thing. Compared to the more 'cuddly' and desirable domestic items, very little industrial and public-service electronic and electrical equipment survives into preservation. When visually attractive items like this surface, they are at risk of being 'upcycled' i.e. turned into useless twee lamps and often deprived of their original functionality. Some systems tend to survive in part only, e.g. here where multiple examples of display instruments exist but the transmitters - unremarkable metal boxes attached to ugly tanks etc - have probably all long since been scrapped.

It would be fun to make a virtual transmitter for some measurable parameter around the house. As it displays up to 144 smaller units that could be hot water cylinder temperature, for example. It almost merits making a water feature where water slowly syphons from one tall tube into another, with the instrument reporting the height of the column. Due to the lucky coincidence between the number of inches in the foot and hours on a timepiece dial, it could serve as an impulse clock. Personally I would think of that as depriving it of its personality, 'downcycling' it from something unusual into the commonplace. Actually that coincidence would be a great risk factor for its survival in the long term, as it would make it extra tempting for the non-enthusiast to gut it and fit a quartz clock movement.

I wonder how many impulses per inch. Is it ten by any chance?

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Old 26th Apr 2022, 8:23 pm   #7
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Default Re: Gent and Co Water level meter

Lucien.
I’m trying not to over restore if as I agree with what you have said.
I did think to myself I could make something up to work with a impulse clock and yes it would be 10 pulses per inch. I have talked myself out of that as I’m not sure the dial coils would appreciate continuous use. It would be good to find some use for it but for the time being when I get a new glass fitted it might just have it on display to I think of a good appropriate use Andy
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Old 27th Apr 2022, 8:40 am   #8
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Default Re: Gent and Co Water level meter

A suggestion - think of the, err, tank in your house which regularly fills and empties with water. Make a sender for it, and amuse yourself every time you, err, empty it (My 'tank' only fills to a depth of 9 or 10", so scaling up the sender so the hands really move might be a nice feature).

I had a colleague who had enjoyed a placement at a very interesting oceanographic place in Liverpool. There they had adapted the faceplate of a similar device, attached to the office toilet. The face once said 'tide level', which had been adapted slightly to retain only the 't' and the 'd' with two other letters in between...
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Old 27th Apr 2022, 10:00 am   #9
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Default Re: Gent and Co Water level meter

Lovely piece, and not pictured in the definitive Gents book by Reynolds.

If nothing else, could you not run it as a slave clock from a suitable master (mechanical or electronic)?
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Old 27th Apr 2022, 10:41 am   #10
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Default Re: Gent and Co Water level meter

Hello Andy,

Just adding a few more diagrams if they are any help. It is a brochure rather than installation manual, but seems to offer extra-ordinary detail for some bits then just a general overview for others.

Regards,

SR
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Old 27th Apr 2022, 11:55 am   #11
Lucien Nunes
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Default Re: Gent and Co Water level meter

Quote:
I’m not sure to transformer is original as it’s not mounted squarely.
As per the drawing, it almost certainly isn't. The device was intended to be connected to GPO private circuits and it was not conventional to include mains circuits inside such apparatus.

Quote:
My 'tank' only fills to a depth of 9 or 10", so scaling up the sender so the hands really move might be a nice feature
One snag is that this is really only designed for slowly-changing levels. Full scale is 1440 impulses. Even 12" on the scale requres 120 impulses, which at say 5 ips would take 24 seconds to respond, by which time the tank might be half-full again.

This rather limited response performance speaks to its technical heritage. Just as Laurens Hammond found another application for synchronous clock parts and concepts in the manufacture of electric organs, so Gents found another application for impulse clock parts and concepts in level transmitters. If you were designing general-purpose telemetry from scratch, you might do it differently and aim for slicker performance and absolute (rather than incremental) indication. But for reservoirs, fuel tanks etc this was adequate.

This is one of the reasons I would not personally use it as a clock. To do so overlooks its own specific chapter of the story and reduces it to something much more commonplace. What I would find interesting would be to put it (measuring a level) and a working impulse slave side-by-side, to show how the common operating principle was applied to serve different purposes.
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Old 27th Apr 2022, 12:06 pm   #12
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Default Re: Gent and Co Water level meter

I would suspect that the float switch transmitter has a local battery supply and would send a dc signal back to the receiver which would be polarity reversed whenever the water level changed from up to down or vise versa.

The voltage may have needed matching to compensate for the distance & subsequent resistance of the telephone line.

The actual clock face would need to be initially manually calibrated in real time to the actual water level in the reservoir by buttons on front ? Once completed, the clock hands would then increment up or down dependent upon polarity of signal received.
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Old 28th Apr 2022, 11:43 pm   #13
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Default Re: Gent and Co Water level meter

Thanks everyone for your thoughts and Stuart for the pictures
I’m surprised that the GPO would approve a device like this.
I would like to know how the float switch control works. There must be a rise and fall switch or contact but how does this work ,also it has to be designed to only give a pulse And not stay on.
It could well be as has been mentioned originally battery. I believe the transformer is a Gents added at a later date but the metal cover is missing.
Andy
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Old 29th Apr 2022, 12:31 am   #14
Lucien Nunes
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Default Re: Gent and Co Water level meter

I have never seen the level transmitter and do not know how it worked, but I know exactly how I would make it work using the techniques of the era and have a strong suspicion the Gents mechanism would have been similar.

Inside the transmitter would be a slave movement exactly like the one in the receiver or recorder. The two would be connected together electrically (with or without relays as described in the blurb) so that the movements in the transmitter and receiver remain in exact synchronism. The two input shafts of a differential gear in the transmitter would be connected to the impulse movement and the float chain respectively, in order to compare the indicated and actual levels. The output would drive a moving contact that could, when rotated beyond a deadband corresponding to about 1/10" from null, make contact with either the 'up' or 'down' fixed contact. This would close a circuit to the appropriate (up / down) wire, or of the appropriate polarity, to advance both movements one step in the correct direction. The impulse movement in the transmitter would drive the differential back to null and open the circuit.

Of course it is quite possible for a sudden movement of the float to require multiple impulses to restore null. Indeed if the float moved full-travel while the power were interrupted, as many as 1440 impulses would have to be counted out exactly to bring the indication back into sync. This requires two provisions. One is to absorb the full travel at the output of the differential gear without losing relative position and while resolving 1/1440 of that travel. This can be achieved without extreme mechanical precision, using a reduction train to operate coincident contacts moving at different resolutions. I.e. the first wheel operates its contact when off null by 1/10" repeating every inch, the second wheel by 1" every foot etc. Only when all are at null, does the circuit open. This is the method used in the Gents programmer / bell ringer albeit in reverse. When the day, hour and minute wheel pegs all coincide, the bell circuit closes for one 30-second impulse cycle. A completely different method that could be used if the contact were very light, would be to absorb the motion in a hairspring while the contact remained against one stop or another.

The other requirement is to impulse the line repeatedly until the null position is restored. This can be achieved by including in the series circuit a slow oscillatory relay, balance-wheel contact or similar, that opens after an impulse long enough for the slave movements to respond. If the slave in the transmitter has driven the differential contact to null, no further impulse is given. If there is still a differential, another impulse occurs when the interrupter re-closes. This is not unlike holding down the manual advance cord in a master clock, while playing the part of the differential comparing the time on your watch to the time displayed on the slave dial in the master clock.

An important aspect of the differential geartrain is that it converts the incremental data (pulse up, pulse down) into an absolute indication of the position of the float. Even if the power is turned off and the float moved to a new position, once power is restored it will drive itself to a correct indication. It will only get out of sync if the battery voltage falls to the critical point where one movement responds but the other does not, or some derangement causes the interrupter to give out misshapen or shortened pulses to which the two movements do not respond alike, or a relayed system without proving contacts loses power at the receiving end only. This limitation is true of all impulse clock systems and requires manual intervention to restore sync.

I should have drawn this, would have saved a thousand words.

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Old 29th Apr 2022, 10:08 am   #15
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Default Re: Gent and Co Water level meter

Quote:
Originally Posted by bionicmerlin View Post
Thanks everyone for your thoughts and Stuart for the pictures
I’m surprised that the GPO would approve a device like this.
I would like to know how the float switch control works. There must be a rise and fall switch or contact but how does this work ,also it has to be designed to only give a pulse And not stay on.
It could well be as has been mentioned originally battery. I believe the transformer is a Gents added at a later date but the metal cover is missing.
Andy
Hi Andy,

The assumed original battery supply would not be an issue for the GPO. I have seen GPO [stamped] Approved PSU's on 1960's alarm signalling equipment connected private wires but clearly this lovely piece of kit predates that.

Rog
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Old 30th Apr 2022, 12:01 pm   #16
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Default Re: Gent and Co Water level meter

I think Andy is lucky with the condition of the timber housing, particularly looking at the condition of the fuse holder...possibly being varnished inside and out has saved it despite damp surroundings.
Dave
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Old 30th Apr 2022, 2:37 pm   #17
Lucien Nunes
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Default Re: Gent and Co Water level meter

Since Andy first posted about this, I have spent some enjoyable hours devising various alternative mechanisms for the transmitter. It is one thing to envisage a scheme that works theoretically, quite another to devise a mechanism that will transmit faithfully after years of unattended operation in arduous conditions. The original Gents transmitter described in the leaflet is chunky and relatively insensitive: It uses a float with a 12lb counterweight and transmits in one-inch increments. Andy's movement responds in 1/10" increments and could therefore give a more precise indication with a more refined transmitter. I have supposed that a general-purpose transmitter is to be designed with the following requirements:

* Ability to resolve, monotonically, all 1440 displayable increments of level
* Avoidance of hunting, double-stepping, generation of runt impulses to which the response of the receiver / recorder cannot be predicted.
* Immunity to cumulative or gross error through rapid float cycling (e.g. waves on liquid), sticking and jerking of the chain, shock and over-tension during maintenance e.g. float cleaning
* Minimum input torque to allow use of small floats with short overall travel
* Reliability under adverse conditions e.g. heat, humidity, dirt and long periods of non-operation with no float movement.
* Minimum power consumption, zero when idle.

Although a simple mechanism is often the best, in this case a simple kind of cam-switch or commutator to select the impulse direction from the difference of the float and repeater positions would demand excessive precision that would be expensive to make, difficult to maintain and intolerant of adverse conditions, vibration etc. It would have to switch from up to off to down by turning through just 15 minutes of arc.

There are three competing designs on the table here at the moment. One is the simplest mechanically but could have contact reliability issues if parts of the float travel are infrequently visited. Another is more complex mechanically but has only one, simple, wiping contact C/O springset.

I recommend this as an exercise for the electromechanical enthusiast.

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Old 2nd May 2022, 2:24 am   #18
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Default Re: Gent and Co Water level meter

Thanks everyone for your input. At least I have learned far more than I expected. For the time being I’m going to get some new glass cut then take it from there. Also the lock has its inner workings and key missing. I sometimes go round antique fairs so could probably pic up a lock from there that’s the same .
Thanks again Andy
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Old 2nd May 2022, 1:02 pm   #19
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Default Re: Gent and Co Water level meter

I would take the lock to bits and get a key cutting shop to measure up the leavers and cut a new key to fit.
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Old 2nd May 2022, 1:50 pm   #20
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Default Re: Gent and Co Water level meter

The leavers are missing inside the lock. I don’t want to replace the lock so I can probably get something similar. I don’t even think key cutting shops do these old keys unless it’s a specialist shop. I have taken locks before to antique fairs and sifted through boxes of keys to find the right ones . Andy
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